The thin film transistor (TFT) adopts a metal oxide semiconductor as the active layer and has the advantages of ultrathin, light in weight, low power consumption etc. Compared with the amorphous silicon TFT, the concentration of carriers of the oxide TFT is ten times of the amorphous silicon TFT. Moreover, the oxide TFT also has the advantages of good uniformity, transparency and simple fabricating process and so on; when it is applied in the array substrate of a display panel, it can meet the requirements of the liquid crystal display (LCD) panel and the organic light emitting diode (OLED) display panel perfectly.
However, the existing array substrate applying the oxide TFT also has the following problems:
Since the water, oxygen and hydrogen groups may permeate to the active layer of the oxide TFT from the passivation layer above the oxide TFT, and cause the threshold voltage of the oxide TFT to shift greatly, thereby influencing the performance of the oxide TFT and even resulting in failure of the product. Hence, the stability and reliability of the array substrate using the oxide TFT need to be improved further.